Sealant having fireworthy properties for use with aircraft parts

ABSTRACT

Fireworthy sealants may have a variety of compositions and be made by a variety of techniques. In certain implementations, a fireworthy sealant may include a body comprised of a cured, tacky, soft, deformable non-adhesive gel. The gel body may have an upper surface, a lower surface, and a perimeter, wherein the upper and lower surfaces of the gel body, in an uncompressed state, define a body thickness. The sealant may, in an uncompressed state, be dimensioned to fit in a first opening between a wall and an aircraft component surface and deformable when under compression to fit in a second opening, smaller than the first opening. The sealant may be flame retardant and produce low smoke density and low smoke toxicity.

RELATED APPLICATIONS

This continuation application claims the benefit of, and priority to,U.S. patent application Ser. No. 16/681,234, (U.S. Pat. No. 10,870,025)filed Nov. 12, 2019 which claims the benefit of, and priority to, U.S.patent application Ser. No. 15/697,266, (U.S. Pat. No. 10,478,649) filedSep. 6, 2017, which claims priority to and U.S. patent application Ser.No. 62/383,889, filed Sep. 6, 2016. These prior applications are hereinincorporated by reference in their entirety.

FIELD OF THE INVENTION

A sealant with flame retardant properties, low smoke density, and/or lowcombustion (smoke) toxicity for use with aircraft components andequipment.

BACKGROUND

Fireworthiness properties, namely, one or more of low smoke density,low-toxicity, and flame retardant properties, are important in themanufacture and maintenance of aircraft. It is a significant challengein design, sourcing, and manufacturing to locate or develop componentsfor manufacturing a gasket for aircraft because of the critical natureof the environment in which they are used. Soft, tacky sealants, whichcan be used as gaskets, have been known hereto, but these do not fulfillall fire protection standards for certain applications.

Aircraft and sealants used with aircraft are constantly thermally cycledand pressure cycled, and the sealants must maintain their effectiveenvironmental sealing properties despite such a radical variation in theenvironment to which they are subject. Sometimes it is hot and sometimescold; and sometimes it is dry, or it is a damp or wet environment with anumber of different chemicals. Acid rain, for example, can be corrosiveespecially when exposed to a metallic aircraft surface. For example, aslight pH change in rain may make it slightly acidic and corrosiveespecially on an aluminum aircraft exterior.

Composite parts used in aircraft construction should comply withstandards related to burning behavior of the material.

Thus, it has been proven to be a challenge to design and manufacturesealants that are acceptable in a wide variety of environments over awide temperature, pressure, and chemical range, which sealants maintaintheir properties and are also, in a fire, non-toxic and flame retardant(or flame resistance). Moreover, what smoke is produced should be of alow density.

SUMMARY

A properly designed part, including a gasket sealant, an injectablesealant, or a tape sealant (collectively a sealant), will help establishsafety for passengers of commercial aircraft especially in event of afire. Such sealants may be used at the interfaces of components toprovide an effective and relatively fire safe seal under a variety ofenvironmental conditions.

The fireworthiness design criteria are related to one or more of theburning behavior of materials, components, subcomponents and systemparts. Fireworthiness as set forth herein refers to the passing of testsfor vertical burn (a measure of flame propagation), smoke density (ameasure of the smoke emitted by a material when burned) and toxicitylimits (the release of noxious and/or harmful gases under flame).Fireworthiness is especially important in use with the interior ofcommercial aircraft.

In some embodiments, Applicant provides a sealant having fireworthyproperties. A fireworthy, adhesive free sealant may include a body and askeleton. The body may encapsulate the skeleton, the body comprising acured, tacky, soft, deformable gel, the skeleton having multipleopenings for encapsulation by the gel body, the skeleton having an uppersurface, a lower surface, and a perimeter, the gel body having an uppersurface, a lower surface, and a perimeter, wherein the upper and lowersurfaces of the gel body, in an uncompressed state, define a bodythickness, the body thickness greater than a skeleton thickness, thesealant in an uncompressed state dimensioned to fit in a first openingbetween the wall and component surfaces and deformable when undercompression from a tightening of the fasteners to a second opening,smaller than the first opening, wherein the sealant is fireworthy.

Smoke toxicity generally tests for leftover components of halogenatedflame retardants, which are harmful in an enclosed area. Smoke densityis an optical test, with the material heated to a certain temperatureand measure the obscuration of a light beam traveling through smokegenerated in a chamber.

The gel used in the fireworthy sealant may be 100% solid (no VOCs). Thefireworthy sealant may have a smoke density Ds of 200 maximum during atest period of about 4.0 minutes under AITM2-0007A, Issue 3, Airbusspecification, published and distributed by Airbus Industries. Thefireworthy sealant may have smoke toxicity limits of less than about:150 PPM HCN, 1000 PPM CO, 100 PPM NO/N0², 100 PPM S0², 100 PPM HF, and150 PPM HCl per AITM 3-0005, Issue 2, Airbus specification, publishedand distributed by Airbus Industries, or FAA Part 25 Appendix E-1equivalent tests. The fireworthy sealant may pass 12 second verticalburn test according to 14 CFR, Part 25-Subpart D, § 25.853 Appendix FPart 1(b)4.

The fireworthy sealant may comprise a two-part polymer, the first partcomprising a polyol and the second part comprising isocyanate, the twoparts when combined curing to form the gel of the gel body. The skeletonof the fireworthy sealant, if used, may comprise a nylon or fiberglass(coated or uncoated with fire retardant) having a thickness less thanabout 0.033″ (0.84 mm). The body of the fireworthy sealant, in someembodiments, may comprise a polyurethane gel in a molecular weight rangebetween about 200 to about 20,000. The tackiness of the fireworthysealant, in some embodiments, may be between about 10 and 30 psi. Thefireworthy sealant may pass the 3000 hour salt fog test according toASTMB 117. The body of the fireworthy sealant may be elastomeric anddeformable under compression. The fireworthy sealant may be elastomericand substantially recover (e.g. greater than 90%) its originaldimensional configuration in a short period of time (e.g., less than oneminute) after 180 days under compression between about 150 and 350 psi.The fireworthy sealant may have a smoke density Ds of 200 maximum at 4.0minutes under AITM2-0007A, Issue 3. The fireworthy sealant may havetoxicity limits of less than about: 150 PPM HCN, 1000 PPM CO, 100 PPMNO/N0 ², 100 PPM S0 ², 100 PPM HF, and 150 PPM HCl under AITM 3-0005,Issue 2. The fireworthy sealant may pass 12 second vertical burn testaccording to 14 CFR, Part 25-Subpart D, § 25.853(a) compartmentinteriors.

The fireworthy sealant may comprise a two-part polymer, the first partcomprising a polyol and the second part comprising isocyanate, the twoparts when combined curing to form the gel of the gel body. The gel bodymay comprise a cured polyurethane gel of molecular weight between about200 and 20,000. The skeleton, in some embodiments, may be eitherpolypropylene, nylon or woven fiberglass and less than about .033″ (0.84mm) thick. The volume ratio of gel body to skeleton may be in the rangeof about 3 to 1 to about 7 to 1. The cured hardness of the gel body maybe between about 40 and 150 measured by 35 gr. cone penetrometer. Thesealant body may further include a corrosion inhibiting composition,such as non-chromate inhibiting compounds.

Devices are provided for achieving an environmental seal to an aircraftassembly comprising a first part and a spaced apart second part, the twoparts forming a gap, the devices comprising sealants having a skeletonand a body encapsulating the skeleton, wherein the body comprises acured polyurethane gel, resulting from a mix of a polyol and isocyanate,the sealant having fireworthiness properties to provide the sealant forpassing the following tests: wherein the sealant has toxicity limits ofless than about: 150 PPM HCN, 1000 PPM CO, 100 PPM NO/N0 ², 100 PPM S0², 100 PPM HF, and 150 PPM HCl under AITM 3-0005, Issue 2; wherein thesealant passes 12 second vertical burn test according to 14 CFR, Part25-Subpart 0, § 25.853(a) compartment interiors; wherein the sealant hasa smoke density of Os 200 maximum at about 4.0 minutes 200 AITM2-0007A,Issue 3. The skeleton may, in some embodiments, be comprised of a nylon,polypropylene or fiberglass mesh having a thickness less than about0.033″ (0.84 mm); and the body may, in some embodiments, have atackiness of between about 5 and 50 psi. The volume of gel/skeleton maybe in the range of about 3/1 to 7/1.

The fireworthy sealants may be tacky but not adhesive to workpiecesurfaces into which they come into contact. They may also be able torelease cleanly (without leaving a residue) after prolonged use undercompression and subject to repeated thermal and pressure cycling.

A method is disclosed for releasably, environmentally sealing a pair ofopposing, gap forming or faying surfaces of aircraft parts, the methodcomprising the steps of: providing an adhesive-free sealant having alayer of polyurethane gel encapsulating a skeleton, the sealant havingfireworthiness properties; placing the sealant in the gap between thesurfaces; and closing the gap, thereby providing a substantially fluidand air tight seal between the opposed mating surfaces with the sealantsubstantially filling the gap; wherein the sealant has a smoke densityOs of 200 maximum at 4.0 minutes under 200 AITM2-0007A, Issue 3; whereinthe sealant has toxicity limits of less than about: 150 PPM HCN, 1000PPM CO, 100 PPM NO/N02, 100 PPM S02, 100 PPM HF, and 150 PPM HCl underAITM 3-0005, Issue 2; and wherein the sealant passes 12 second verticalburn test according to 14 CFR, Part 25-Subpart 0, § 25.853(a)compartment interiors.

The sealant of the providing step may have a tackiness, in oneembodiment of between about 5 and 50 psi or a peel strength of about Oto 5 piw. The method may also include tightening of fasteners betweenthe opposing surfaces until the sealant visibly deforms. The body mayinclude a polyurethane gel with a molecular weight range between about200 to 20,000. The sealant may pass the 3,000 hour salt fog testaccording to ASTMB 117. The body of sealant may be elastomeric; whereinthe sealant substantially recovers at least 50% of its originaldimensional configuration after compression between about 150 and 350psi for 180 days in less than one minute. The skeleton may be nylon,polypropylene (which may be molded), or coated or uncoated wovenfiberglass and less than about 0.033″ (0.84 mm) thick.

In certain implementations, a non-adhesive sealant may include a bodycomprised of a cured, tacky, soft, deformable gel, the gel body havingan upper surface, a lower surface, and a perimeter, wherein the upperand lower surfaces of the gel body, in an uncompressed state, define abody thickness. The sealant may, in an uncompressed state, bedimensioned to fit in a first opening between a wall and an aircraftcomponent surface and deformable when under compression to fit in asecond opening, smaller than the first opening. The sealant may have asmoke density less than 200 after about 4 minutes of exposure to theflame-only smoke density test in AITM2-0007A, Issue 3. The gel of thesealant may be 100% solid (no VOCs).

In some implementations, the sealant may including a skeletonencapsulated by the body. The skeleton may have multiple openings forencapsulation by the gel and have an upper surface, a lower surface, anda perimeter, wherein the upper and lower surfaces of the skeleton definea skeleton thickness, the skeleton thickness being less than the bodythickness.

In certain implementations, the sealant may have toxicity limits of lessthan about: 150 PPM HCN, 1000 PPM CO, 100 PPM NO/N0 ², 100 PPM S0 ², 100PPM HF, and 150 PPM HCl under AITM 3-0005, Issue 2. Additionally, thesealant may pass the 12 second vertical burn test according to 14 CFR,Part 25-Subpart D, § 25.853(a) compartment interiors. The sealant mayalso pass the 3000 hour salt fog test according to ASTMB 117.

The sealant may be composed of a two-part polymer, the first partcomprising a polyol and the second part comprising isocyanate, the twoparts when combined curing to form the gel of the gel body, and whereinthe skeleton is comprised of a nylon or fiberglass having a thicknessless than about 0.033″. In certain implementations, the body may becomposed of a polyurethane gel with a molecular weight range betweenabout 200 to 20,000. The sealant may also have a tackiness between about20 and 30 psi.

The sealant may quickly (e.g., in less than one minute) recover most itsoriginal dimensional configuration (e.g., greater than 90%) aftercompression between about 150 and 350 psi for 180 days. The volume ratioof gel body to skeleton may be in the range of about 3 to 1 and 7 to 1.The cured hardness of the gel body may be between about 40 and 150measured by 35 gr. cone penetrometer. The body may further include acorrosion inhibiting composition.

In particular implementations, one or more sealants may be resistant todegradation upon exposure to common aviation fluids.

In a preferred embodiment, the sealant is adhesive free. Adhesivescreate high strength bonds to the mating surfaces making clean releaseand reuse difficult. Sealants typically have a lower bonding strengthbut create substantially air and fluid tight contact with the matingsurface or surfaces.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a gasket sealant according to thepresent specification.

FIG. 1A is an elevational view of a gasket sealant with an impervious,tack and adhesive-free sheet on a surface thereof.

FIG. 2 shows a tape sealant according to the present specification.

FIGS. 3A and FIG. 3B are illustrations of skeletal structures that maybe used in application's sealant.

FIG. 4 illustrates an apparatus for testing smoke density and smoketoxicity.

FIG. 4A illustrates a sealant undergoing vertical flammability testing.

FIGS. 5 and FIG. 6 illustrate Smoke Density results of the same productssubject to the flammability and Smoke Toxicity tests.

FIGS. 7A, 7B, 7C, and 7D illustrate a test coupon after a 3000 hour saltfog test with a fireworthy gasket made according to the specificationset forth herein.

FIGS. 8A, 8B, 8C, and 8D illustrate a use of Applicant's sealant withfloorboard assemblies of an aircraft interior.

FIGS. 9A, 9B, and 9C illustrate an assembly and procedure to testphysical characteristics of Applicant's sealant.

FIGS. 10A, 10B, 10C, 10D, and 10E are illustrations of the testapparatus probe engaging the sealant during test for tack, work ofadhesion and cohesion.

FIGS. 11A and 11B are graphs of the results of FIGS. 10A-10E tests.

FIG. 12 illustrates a manner of making a sealant described herein.

FIGS. 13A-B illustrate examples of an injectable sealant according tothe present specification.

FIGS. 14A and 14B illustrate an Aviation Fluids Exposure Test fortesting Applicant's sealants.

FIG. 15 illustrates another example use of an injectable sealant.

FIG. 16 illustrates example test results for a vertical burn test.

FIG. 17 illustrates example test results for a smoke density test.

FIG. 18 illustrates example test results for a smoke toxicity test.

DETAILED DESCRIPTION

Fireworthiness in a sealant means: the sealant (e.g., gel body andskeleton) passes all three of a flammability test, a smoke density test,and a smoke toxicity test. The flammability test is vertical burn,compartment interiors and is conducted pursuant to FAR 25.853(a)Appendix F, Part I, (a), 1, (ii): 12 sec. The smoke density test(Determination of Optical Smoke Density of Component Parts orSub-Assemblies of Aircraft Interiors) is performed pursuant toAITM2-0007A, Issue 3 (flaming mode only). The smoke toxicity test(Determination of Specific Gas Components of Smoke Generated by AircraftInterior Materials) is conducted in accordance with AITM3-0005, Issue 2.In certain implementations, the sealant may pass one (e.g., smokedensity or smoke toxicity) or two (e.g., flammability and smoke densityor flammability and smoke toxicity) of these tests.

The fireworthy sealant should be an effective, non-adhesive,environmental seal. An effective environmental seal means substantiallyair and moisture proof and that the sealant substantially retains, insome embodiments, a tackiness of at least about 50% of the originaltackiness after 90 days under a compression of between about 150 psi-350psi.

In some embodiments, the sealant does not include: an adhesive or anadhesive layer, foam (or air bubbles), water (less than 1% water byweight and by volume), silicone or silicone oil, leachates (undercompression the leachates may cause staining to an aluminum alloyworkpiece), processing oil, VOC's (volatile organic compounds) orSemi-VOC's, tackifiers or low molecular weight (liquid) materials. Insome embodiments, part or all of the external surfaces of the sealantcomprise the material of the encapsulating body itself (that is, no“skin” and no “adhesive layer” forming an outermost part).

The gel body of the sealant both encapsulates the skeleton andreleasably bonds to opposed workpiece surfaces (unless a PTFE skinused). Typically, no adhesive layer is used as found in some prior artgaskets. In some embodiments, the skeleton may be nylon, polypropylene,or woven fiberglass, i.e., without a fire retardant coating.

Other potential skeletons include metal meshes, where mesh includeseither open or closed fabrics, cloths, webs, screens, or meshes.Skeletons could also be metal wire screens or metal-plated fabricsheets. The mesh may be inherently conductive if it is formed from, forexample, metal, metal alloy, graphite, or carbon. A mesh may also beconstructed from monofilaments, yarns, bundles, or other fibers. A meshmay also be inherently non-conductive but made conductive by an appliedcoating, plating, sputtering, or other appropriate treatment ofelectrically conductive material.

Examples of inherently conductive materials include copper, nickel,silver, aluminum, steel, tin, bronze, and alloys of the above. Potentialalloys, for example, include monel nickel and copper alloys. Otherinherently conductive materials include carbon, graphite, inherentlyconductive polymers, plated or clad wires, silver-plated copper,nickel-clad copper, and Ferrex, tin-plated, copper-clad steel, tin-cladcopper, tin-plated phosphor bronze, and fibers of any of the abovematerials.

Examples of inherently non-conductive materials include cotton, wool,silk, cellulose, polyester, polyamide, nylon, polyimide monofilaments oryarns. These materials may be plated, coated, or otherwise madeconductive by application of one of the “inherently conductive”materials listed above. The plating, cladding, or other coating processmay be done to individual strands, to the surface after weaving,knitting, or other fabrication.

Other combinations of the above materials may also be employed. Forskeleton materials having problems passing the fireworthy tests, smallerportions of the materials may be used in certain implementations.

The sealant body is tacky. Tack is a property of a sealant whereby lightcontact with the surface of another body brings about a conditionrequiring force to restore the original separated state. It is aproperty that will inhibit but not wholly prevent the removal of acontacting surface or surfaces, such as opposing walls of aircraft partscontacting the sealant under compression. Inherent tack means the gelpossesses this property (tack) without requiring the addition of anyfurther adhesion promoting component, or a tackifier.

Adhesive based products and gel based sealants differ on several scales.One of them is not only what their intended use is, but also in theirbasic structures, bonding, and physical characteristics. Adhesivesprovide a more permanent, rigid and durable bonding as opposed tosealants, such as gels, which are lower in strength and far moremalleable. Sealants are typically not used to bond things permanentlytogether. Adhesives have more power for holding and bonding, butsealants are good for air and water tight spaces and as gap fillers.Sealants have lower bonding strength and a higher elongation percentagethan adhesives. Sealants are meant to provide a watertight seal, but areeasily removable when necessary. Adhesives typically are not meant to beremoved.

Applicant's fireworthy sealants when used with aircraft parts typicallyachieve at least three results: substantially fill a gap (little to noair or moisture) between opposing mating surfaces, form a physicalbarrier to fluid and gaseous migration through the gap at thesealant/workpiece surface and maintain their sealing properties over anexpected lifetime under a variety of service conditions (including −65°C. to 85° C.) of at least 180 days, and up to 1.5 years, or longer.

The sealant 10 (gasket)/26 (tape) designated, SD #5, used forfireworthiness testing is a gasket (see FIG. 1 ) that may be made from atwo-part polyurethane gel from KBS Chemical (KBS Chemical, Dodd City,Tex. (U.S.A.)), and may be about 3″ long, 2″ wide, about 0.040″ (1.0 mm)thick (uncompressed). The gel body may be comprised of a two-parttypically 50/50 mix (by volume) of a polyol and an isosynate (KBSChemical, Part Nos. P-1025 and N-1024). The gasket is manufactured, incertain embodiments, generally, according to U.S. Pat. Nos. 6,530,577,6,695,320 and 7,229,516 and U.S. Patent Publication Nos. 2004/0070156and 2004/0041356, (incorporated herein by reference), with, however, thegel being as set forth herein and the skeletal material as set forthherein. A body 12, in some embodiments of cured polyurethane, may benon-reactive to aluminum and, in particular embodiments, other aircraftmaterials and provides a tacky outer surface that is integral to thesurface—meaning, no skin is provided, the polyurethane gel body isexposed at the workpiece surface or surfaces. It may have servicetemperature limits of about −65 Q C to 135 Q C (meaning it substantiallyretains its functional properties) and passes 3000+ hour salt spray test(ASTM B117). In some embodiments, body 12 may be a polyurethane gel witha hardness in the range of about 40-150 on 37.5 gr. half conepenetrometer.

The skeleton used for the tests is, in some embodiments, a molded orextruded, non-knitted nylon available from Conwed of Minneapolis, Minn.(U.S.A.) as part number NL-1400, is about 0.015″ thick with 20 strandsper inch. A similar molded or extruded polypropylene may also be used.In a preferred embodiment, the skeleton is a non-knitted nylon less thanabout 0.033″ thick, or between about 0.008″ and 0.026″ thick. In anotherembodiment, the volume ratio of polyurethane gel/skeleton ranges are inthe range of about 2/1 to 7/1 more preferably 3/1 to 6/1, preferablyabout 4.5/1 to provide fireworthiness.

This specification describes a fireworthy gasket 10 (FIG. 1 ) or afireworthy tape 26 (FIG. 2 ) (together “sealant”), both as noted hereincomprising a body 12 and a web or skeleton 14 as seen in FIGS. 1, 1A, 2,3A and 3B. Body 12 is typically sheet-like, or tape typically with W andL»T, and skeleton 14 is typically bendable along its W and L axes. Body12 may have a tacky polyurethane top surface 16 and a spaced apart,tacky polyurethane bottom surface 18. Typically, the body encapsulatesthe skeleton and there are no visible air bubbles. Gasket 10 or tape 26may include outer perimeter or walls 20 and inner perimeter or walls 22defining, optionally, fastener holes 24. In one embodiment (see FIG.1A), a skin 30 may be interposed on one (top or bottom) or both surfacesof the body, which skin 30 may be intended to be part of the gasket,that is to say, is intended to be under compression between a platformand a workpiece. In one embodiment, skin 30 is a thin sheet of PTFE. Ina preferred embodiment, there is no skin, the gel body includes the topand bottom surfaces that contact the workpiece. A release film 28 may beprovided for adherence to the top 16 and/or bottom 18 surfaces, whichrelease film prevents the tacky polyurethane surfaces from inadvertentlyadhering to objects prior to removal and use. Release film 28 isintended for removal prior to use between a workpiece and a platform orbase, that is to say, before interposing the gasket between matingsurfaces.

FIG. 1A illustrates a gasket having a skeleton and a skin 30 comprisinga PTFE sheet. The PTFE sheet is applied to one side of the body of thegasket. The PTFE sheet sticks to the one side of the gasket. With thePTFE sheet on one side of the gasket and the other side of the gaskethaving a body exposed to the workpiece, for example, two aircraft partsunder compression, the side of the gasket having the PTFE sheet isnon-tacky to the workpiece. This then become a gasket with only a singleface tacky to the workpiece. A gasket such as this may be used inembodiments where selective release to one side is desire. Anotherenvironment, where only one side of a gasket requires a goodenvironmental seal (sticky side to the workpiece) a gasket such as thesingle sided sticky gasket illustrated in FIG. 1A may be sufficient.There are other types of sheets that may be sticky to the gasket andnon-sticky to the workpiece, PTFE being only one example.

Applicant provides, in some embodiments, a non-knitted, non-wovennet-like skeleton 14 with multiple open pores defined by strands 34joined at joints 36 (see FIGS. 1, 2 and 3A). In another embodiment, seeFIG. 3B, the skeleton may be a woven or knitted material with strandscrossing and touching instead of being joined (“fused”) such as wovenmonofilament nylon or woven multifilament nylon 15 or woven or knittedfiberglass. In one embodiment, the sealant consists of body 12 andskeleton 14. In another embodiment, the sealant consists essentially ofbody 12 and skeleton 14.

FIG. 3A shows a molded or extruded, non-metal, plastic skeleton such asa synthetic or semi-synthetic polyamide, in one embodiment, nylon. FIG.3B shows a skeleton that is woven or knitted and may also be from thesame materials and have the same properties as set forth herein.

The various gaskets, tape, and injectables of the instant disclosure maybe used for numerous applications on an aircraft and, in someembodiments, a railroad car, a ship or other waterborne vessels. Theaircraft uses include, but are not limited to: fuel access door gaskets,aircraft floor panel gaskets (see FIGS. 8A-8D), aircraft antennagaskets, cargo bay, galley and surge plate environments. Injectables maybe used in seat track channels (See FIG. 15 ) or where wires or conduitspenetrate an aircraft wall (See FIGS. 13A-B).

Applicant has tested for flame travel and smoke density on fiberglassmesh of about 0.015″ (0.38 mm) thickness that is used for screenpurposes, such as in windows and doors. It appears to generatesignificantly more smoke than coated fiberglass mesh. Wire mesh, such asa woven metallic aluminum or other metal skeleton, may be used, such as0.11 to 0.25 mil aluminum alloy. A woven nylon cloth would work as asuitable skeleton, based on initial tests. Both of these products may,in some embodiments, be in the gel to mesh ratios indicated. Otherexample skeleton materials include nylon, polypropylene, polyethylene,and PTFE.

FIG. 4A illustrates Example 1, wherein Applicant provides a sealant10/26 that in the Vertical Flammability test is approximately 3″ by 12″about 0.099 oz. In the Smoke Density and Smoke Toxicity tests, thesealant 10/26 is 2.9″ by 2.9″ and weighs about 0.023 oz.

FIG. 12 illustrates sealants may be made using an applicator 66, such asa 200 mil dual component cartridge for dispensing sealants, such as aPower Push 7000 by Meritool. Applicator 66 comprises two compartments,one for receiving a first part, such as a polyol 12 a, Part No. KBSP-1025, and a second for receiving a part, a urethane component providedby an isocynate 12 b, such as Part No. KBS U-1024. The two parts may mixin nozzle 68 thoroughly and flow as a syrupy mass uncured gel mix 12a/12 b onto a support surface, such as a flat glass table, with arelease film thereon, so that they coat and encapsulate mesh 12 and cure(between about 30 and 90 minutes) for removal from the release sheet.The sealants tested 10/26 may be about 0.0365 oz. per square inch at 44mil thickness. This corresponds to a weight of about 0.0338 oz. persquare inch for the gel and about 0.0027 oz. per square inch for themesh. The mesh used was the Conwed mesh referenced herein.

The gel was poured to about 44 mil thickness. The manufacturing stepsare substantially as set forth in U.S. Pat. Nos. 6,530,577; 6,695,320;7,229,516; and US 2003/0234498. The gel mix 12 a/12 b is best appliedwith a crisscross or zigzag pattern overlapping the ends of theskeleton, which excess gel, after curing, can be cut with a razor andremoved or otherwise trimmed. Any visible bubbles should be worked outwith fingers after laying on a release sheet. Excess material may besqueegeed off before curing.

Testing on similar gaskets placed under a torque of between about 15 andabout 35 inch pounds for over six months have shown clean separationbetween two aluminum alloy aircraft pieces and showed that the sealantrecovered to about 40% to 90% of its original thickness and shape, didnot dry out, maintained its structural integrity and other chemical andphysical properties including but most of its tackiness, and provided aneffective environmental seal. In certain embodiments, the sealant willrecover the majority of its original shape (e.g., greater than 75%) inless than three minutes, and in some embodiments, the sealant mayrecover most of its shape (e.g., greater than 90%) and/or recover itsshape in less than one minute. In particular implementations, the gasketmay recover close to all of its original shape (e.g., greater than 99%).Moreover, the surface tackiness allowed it to maintain its reusability,allowing multiple releases and resealing of the same sealant.

FIGS. 13A-B illustrate examples of an injectable sealant 13. Sealant 13may be similar in composition to the body of gasket 10. For example,sealant 13 may be a two-part, polyurethane gel (e.g., mix of polyol andisocyanate). Sealant 13 typically does not includes a skeleton, however.Sealant 13 may be fireworthy (i.e., pass all three tests), pass two ormore of the fireworthy tests (e.g., flammability and smoke density), orjust pass one of the fireworthy tests (e.g., smoke density).

In FIG. 13A, sealant 13 is being applied from a two-part applicator 66′to a cavity 70 formed by an aircraft component Ac. Although cavity isshown here as being fairly wide compared to its depth, cavity 70 maygenerally take the shape of any partially enclosed structure (e.g., abasin, a gap, or a crack). As illustrated, sealant 13 may be applieddirectly into cavity. Due to its viscosity, sealant 13 may self level(e.g., fill the cavity from the bottom up). Depending on how muchsealant is applied, sealant 13 may fill all or part of cavity 70. Afterapplication, sealant 13 will cure (e.g., form in place) in cavity 70,forming a seal to the edges of the cavity and around conduit 72.

FIG. 13B shows two-part sealant 13 cured in a cavity 70′, formed by anaircraft antenna Aa, gasket 10, and an aircraft skin As. As mentionedabove, due to its viscosity, sealant 13 has self-leveled in cavity 70′.

In FIG. 15 , sealant 13 has been applied to an aircraft seat track 72.Seat track 72 may, for example, be made of an aluminum alloy and, asillustrated, includes a channel 74 in which lower mounts for aircraftseats may be inserted and adjusted. Without some type of sealant,channel 74 may remain open catch debris. Sealant 13 may be applied froma two-part applicator to channel 74. Due to its viscosity, sealant 13may self level (e.g., fill the cavity from the bottom up). Depending onhow much sealant is applied, sealant 13 may fill all or part of channel74. After application, sealant 13 will cure (e.g., form in place) inchannel 74, forming a seal to the sides and bottom of the channel.

Sealant tested was 2″×3″ (Smoke Density and Toxicity) sealant designatedSD #5 with a thickness about 0.040″ (1.0 mm). It has a thin nylon meshskeleton or carrier about 0.015″ (0.38 mm) thick, part NL-1400 (Conwed,www.conwedplastics.com) white, pattern/Design 20. The body is composedof a two part cured polyurethane gel, 50/50 mix of polyol and isocynate,KBS Chemical, Part Nos. U-1024 (urethane) and P-1025 (polyol). Thissealant passed all three fireworthy tests.

Fire Retardant Chemicals for use with polyurethane include hydratedmetal compounds and phosphorous flame retardants. In the presentinvention, the flame retardant added to the polyurethane gel is notparticularly limited, but a halogen-free flame retardant which does notproduce a toxic halogen gas is preferred.

Examples of hydrated metal compound based flame retardants includealuminum hydroxide, aluminum oxide hydroxide, magnesium hydroxide,calcium hydroxide and the like. Examples of the inorganic compound basedflame retardant include antimony compound, zinc borate, zinc stannate,molybdenum compound, zinc oxide, zinc sulfide, zeolite, titanium oxide,nano filler (montmorillonite (MMT), nano hydrated metal compound,silica), carbon nanotube, calcium carbonate and the like.

Examples of phosphorus flame retardants include phosphates, aromaticcondensed phosphates, ammonium polyphosphates and the like. Specificexamples of the phosphate include triphenyl phosphate, tricresylphosphate (TCP), cresyl diphenyl phosphate (CDP), 2-ethylhexyldiphenylphosphate, triethyl phosphate (TEP), tri-n-butyl phosphate, trixylenylphosphate, xylenyl diphenyl phosphate (XDP), triphenl phosphate (TPP),isopropylated triphenyl phosphate (IPTPP), tris (p-t-butylphenyl)phosphate (TBPP), and the like. Specific examples of the aromaticcondensed phosphate include resorcinol bisdiphenyl phosphate, bisphenolA bis(diphenyl phosphate), resorcinol bisdixylenyl phosphate and thelike. Specific examples of the ammonium polyphosphate include ammoniumpolyphosphate (APP), melamine-modified ammonium polyphosphate and coatedammonium polyphosphate. Here, the coated ammonium polyphosphate isobtained by coating or microcapsulating ammonium polyphosphate with aresin to enhance water resistance. The phosphate, aromatic condensedphosphate and ammonium polyphosphate can be used concurrently.

Examples of silicone flame retardants include dimethylsilicone,amino-modified silicone, epoxy-modified silicone and the like.

Examples of nitrogen compound based flame retardants include hinderedamine compounds, melamine cyanurate, triazine compounds, guanidinecompounds and the like.

Examples of organic metal compound based flame retardants include copperethylenediaminetetraacetate, calcium perfluorobutanesulfonate and thelike.

Examples of proprietary flame retardant mixtures include: EmeraldInnovation NH-1 from Great Lakes Solutions of Middlebury, Conn.(U.S.A.), Fyrol HF-5 from ICL Industrial Products of Beer-Sheva, South(Israel), Firemaster 500® or 600® (Halogenated) from Great LakesSolutions, Exolit AP-740 from Clariant of Muttenz, Basel-Country(Switzerland), Antiblaze PR82 from Albemarle Corporation of Charlotte,N.C. (U.S.A.).

Other examples of flame retardants include: Expandable graphite,melamine, phosphoric acid, Borax, clays, mesophorus silicate.

One or more kinds of the flame retardants may be used typically aspowder added in a mixture on the polyol side or the isocyanate side orboth sides (that is, before the two are mixed in applicator nozzle).While the amount to be used may be varied depending on the kind of theflame retardant or the desired physical characteristics of the resultingsealant, in some embodiments, it is preferably not less than about fiveparts by weight, more preferably not less than ten parts by weight,particularly preferably not less than twenty parts by weight, relativeto 100 parts by weight of the total polyol plus isocyanate (gel) mix 12a/12 b. Here, the powder may be premixed in the polyol and isocyanatethe two parts mixing in an applicator nozzle. In one embodiment, the twoparts will set up (to about 90% final hardness) within 30 minutes uponmixing.

TEST 1

FIG. 16 illustrates example test results for a vertical burn test inaccordance with FAR 28.853 Appendix F, part I, (a), 1, (ii): 12 sec.(same as ABO 0031) (FIG. 4A illustrates the test apparatus and testsetup).

Vertical burn test is used for cabin and cargo compartment materials onaircraft may utilize a Bunsen burner 42. This test is intended for usein determining the resistance of materials to flame when testingaccording to 60 second and 12 second vertical Bunsen burner tests asspecified in FAR 25.853 and FAR 25.855. Ignition time is the length oftime the burner flame is applied to the specimen 10/26 and may be either60 or 12 seconds for this test. The flame time is the time in secondsthat the specimens continue to burn after the burner flame is removedfrom beneath the specimen. Surface burning that results in a glow butnot in a flame is not included. Drip flame time is the time in secondsthat any flaming material continues to flame after falling from thespecimen to the floor of the chamber. If no material falls from thespecimen, the drip flame time is reported to be zero seconds and thenotation “No Drip” is also reported. Burn length is the distance fromthe original specimen edge to the farthest evidence of damage to thetest specimen due to that area's combustion including areas of partialcombustion, charring or embrittlement, but not including areas sooted,stained, warped or discolored, nor areas where material has shrunk ormelted away from the heat.

TEST 2

FIG. 17 illustrates example test results for a smoke density test. FIGS.5 and 6 graphically illustrate the results.

FIGS. 5 and 6 are graphs for specific optical density versus time.Specific optical density is a dimensionless measure of the amount ofsmoke produced per unit area of a material when it is burned. In thistest, the maximum value of Ds that occurs during the first four minutesof a test, Dm is reported. A photometric system including amicrophotometer and a photomultiplier is typically used in a smokedensity chamber. A recording device is used to record the percentage oflight transmission for optical density versus time during the test.

The test chamber, radiant heat furnace, heat flux density gauge,specimen holders, photometric system and multidirectional pilot burner,etc. are used in the manner as defined in the test specifications. Thetest chamber may be a square-cornered box, with inside dimensions about914 mm in width, 610 mm in depth, and 914 mm in height, and a sealingdoor that allows a small positive test pressure to be developed. Theinside surface of the test chamber may be porcelain-enameled metal(e.g., steel) or equivalent coated metal that is resistant to chemicalattack and corrosion.

The photometric system used consists of light source and aphotomultiplier to mounted vertically, with a photomultipliermicrophotometer that converts the photomultiplier tube output either tointensity and/or optical density, with a strip chart recorder or othersuitable recording means to record light transmission versus time.

The pilot burner may have six tubes, each with an inside diameter ofabout 1.4 mm and an outside diameter of about 3.2 mm), that are fed witha filtered, oil-fee air at a flowrate of about 500 cm³/min and at least95% purity propane at a flow rate of about 50 cm³/min, both flow ratesreferenced to 23° C. and 1013 hPa. The ends of two of the tubes may beperpendicular to the exposed face of the specimen, the ends of two ofthe other tubes may be at a 45 degree angle to the ends the first twotubes, and the ends of the other two tubes may be at a 90 degree angleto the ends of the first two tubes. The tips of the pilot burner's tubesthat are perpendicular to the exposed face of the specimen may bepositioned about 6.4 mm from the face of the specimen. The tubes maygenerate flamelets with a visible part about 6 mm long and a luminousinner cone about 3 mm long.

Smoke density Ds can be calculated according to the following:

$D_{s} = {\frac{V}{L*A}{Log}_{10}\frac{100}{T_{t}}}$Where:

-   -   Ds=optical smoke density    -   V=chamber volume    -   L=light path length    -   A=exposed specimen area    -   Tt=percent light transmission at the time tin minutes    -   Log10(100/T,)=optical density at time t.        Smoke density can be an average density over several samples        (e.g., three).

TEST 3

FIG. 18 illustrates example test results for a smoke toxicity test.

In general, smoke and toxicity gases should be harmless and not releasedin significant quantities.

In a Smoke Density Chamber, gaseous/volatile test products are drawnfrom the chamber at any time for analysis. This test method is used forevaluating materials or constructions used in the interior of aerospacevehicles, but may be utilized for other applications as specified inapplicable procurement and regulatory documents. It is used to measureand describe the properties of materials, products or assemblies inresponse to heat and flame under controlled laboratory conditions.Results of this test may be used as elements of a fire risk assessmentwhich takes into account all of the factors which are pertinent to anassessment of the fire hazard of a particular end use. One NBS SmokeDensity and Smoke Toxicity chamber that may be used for these tests isGovmark Model SD-2 (see FIG. 4 ).

TEST 4

Test Results: Salt Fog (Corrosion Resistance)

The Salt Fog Test (FIGS. 7A, 7B, 7C, and 7D) is a standard corrosiontest ASTMB 117 and is used to verify corrosion resistance of sealants.The appearance of corrosion products, such as oxidized aluminum, isevaluated, typically visually, after a predetermined period of time, forexample, 3000 hours. The apparatus uses typically a closed cabinet orchamber wherein a salt water (5% sodium chloride) solution is atomizedby means of spray nozzles. This produces a dense salt water fog mist orspray in the chamber and subjects the test coupon with specimen 10/26 toa severely corrosive environment. In FIGS. 7A-7D, the coupon is 2 inchesby 3 inches made according to the gel body and skeleton set forth hereinwith respect to the fireworthiness properties and was exposed to 3000hours of salt fog testing. FIGS. 7A and 7D illustrate the protectedportions of the aluminum coupon and the visible absence of the corrosiveoxidation (substantially clear) that is seen in the mottled look(oxidized aluminum) of the exposed areas of the coupon. This isconsistent with effective environmental sealing. Moreover, after suchexposure, the tackiness between the aluminum and the sealant was atleast about 50% or greater than the initial tackiness

TESTS

This establishes Applicant's standard test method for evaluating thetack of polyurethane gel sealant products, and work of adhesion andcohesion.

Test Assembly

This test assembly (see FIGS. 9A, 9B, and 9C) consists of a testspecimen 10/26. The test specimen is typically a 1″×6″ sample of apolyurethane gel sealant material. The test specimen is tested at atemperature of 73.4±3.6° F.

Texture Analyzer is a machine 52 that measures a number of variables,including tack, work of adhesion and cohesion of the sealant surface,when a probe moves upward from a downward deflected surface position,caused by probe 50. Applicant uses a Texture Technologies TA.XT pluswith a 50 kg load cell (Texture Technologies, Hamilton, Mass., seetexturetechnologies.com). See FIGS. 10A and 10C for Applicant's typicalmachine setup. The calibration weight is a precision mass of 200 gr.used for calibrating the load cell.

Procedure

Open the Exponent program, select a user, and click OK.

Calibration Procedure: Three calibrations shall be done beforetesting—height, force, and frame stiffness.

Height: To calibrate height, clear the texture analyzer of any testingmaterials. ClickT.A.>Calibrate>Calibrate Height, enter the followingvalues: Return Distance—10, Return Speed—10, Contract Force—1000, andthen click OK.

Force: To calibrate force, clear the texture analyzer and thecalibration platform of any testing materials. ClickT.A.>Calibrate>Calibrate Force>Next, enter the weight of the calibrationweight to be used, place the calibration weight on the calibrationplatform, click Next, remove the calibration weight, and flick Finish.

Frame Stiffness: To calibrate frame stiffness, clear the texture of anytesting materials and ensure the proper load cell is installed. ClickT.A.>Calibrate>Calibrate Frame Stiffness, enter Max Force—90% of theload cell capacity and Speed—0.01, click OK, and click OK again.

Testing Procedure: To open the project, click File>Project>Tack. Clickthe test configuration button and enter the name of the test in theInput File ID box, typically with the following format: Name ofmaterial—thick/thin side—Person who show the material—Front, Middle, Endsection of the table (for example, HTB—TN—SW—EN—). Enter the batchinformation in the Batch box typically with the following format: #LotNumber-Carrier Lot Number (for example, #5037-M151 ?B). Ensure that theAutoSave is checked and the file path is correct so that it will save tothe proper folder (see FIG. 10B for typical test configuration). Removerelease film on side of sample to be tested and apply the sample to thetest specimen panel. Slide the test specimen panel into the base unitand tighten down in the spot to be tested. Clean the probe tip with apaper towel moistened with isopropyl alcohol. To begin the test, clickRun Macro>Yes.

The test shown in FIGS. 9 Series, 10 Series, and 11 Series is formeasurement of: tack, work of adhesion and cohesiveness. Force ismeasured as the probe goes up from the initial position (FIG. 10C). Thefoot of the probe (silver coated stainless, area—0.06 sq. in.) ispressed into the material (FIG. 10A) a certain distance at a certainspeed and then retracted at that same speed. The force is measured onthe upward retraction stroke only (FIGS. 10B-10E) to measure the “tack”of the material. Tack is the maximum point on the force vs displacementcurve, the peak value. It measures the maximum amount of force needed(or psi when foot area is taken into consideration) to separate theprobe from the material. The work of adhesion is the total area underthe curve of FIG. 11A (above the X axis). This property should haveunits of lb-in (force*distance). It measures the total amount of workdone (energy expended) by the retracting force involved in separatingthe probe from the material (FIG. 10E).

Cohesiveness is the tendency of the material to stick together. Forexample: taffy is more cohesive than bread. The cohesiveness is measuredas the ratio of the area of the right half A2 of the curve of FIG. 11Ato that of the left half A1 of the curve with the maximum force point(tack) defining the boundary. If adhesion is low compared with cohesion,then the probe is likely to pull off the specimen easily and to remainclean as the product has the ability to hold together. If adhesion ishigh, out of the maximum range, then sealant is in the range ofadhesives.

A graph of the tack test for the fireworthy products subject to Tests1-5 (Applicant's sealant SD #5) and another polyurethane gel andfiberglass skeleton coated with fire retardant (without fireworthiness)designated HT3935-7 similarly dimensioned (FIG. 11B) for reference.

Work of Tack Adhesion Cohesiveness SD#5 0.91 0.051 1.188 HT3935-7 1.3780.069 0.89Results

Following this test method will result in a graph that will record thefollowing—Tack (lb/in²); Work of Adhesion; Cohesiveness.

-   -   Applicant measured the following values:

Cohesiveness 0.516 Work of Adhesion 0.948 pound inches Tack 26.915pounds/sq. in. (or about 1.4 pounds on a probe with contact area ofabout 1/16 sq. in.)

-   -   Acceptable ranges:    -   Tack: 20-30 psi (most preferred), 15-45 psi, 5-50 psi    -   Work of Adhesion: 0.5-5, 0.1-10    -   Cohesiveness: 0.25-1, 0.1-3, 0.1-5

TESTS

Test Results: Aviation Fluids Exposure Test

Photograph each test assembly (see FIG. 14A, base assembly 44,application FIG. 14B), weigh on an analytical balance, and record theresult. Hang test assembly on the spray rack (see FIGS. 14A and 14B).Spray test assembly with test fluid TF from spray bottle 48 every 4hours for 8 hours, allow to dry for 16 hours and then repeat this cycletwo more times. Spray each bare test assembly 44 including sealant 10/26(FIG. 14A) with nitrogen to remove excess fluid from mesh backing ifnecessary. Wipe each in-application (aluminum alloy coupon) testassembly 46 including sealant 10/26 (FIG. 14B) with a paper towel toremove excess fluid from coupons if necessary. Photograph each testassembly and weigh on the analytical balance and record the result aftereach 16 hour dry period. Also, visually note and record any changes intest specimen throughout testing.

Ideally, there should be no fluid on the samples after the drying periodand the physical drying before weighing. In practice, there may be somesmall amount of fluid left on the sample, but may be considered to be“in the noise” and negligible.

The following data is from Applicant's fluids TF exposure test on thefireworthy sealant. The sealant material is sprayed with variousaviation fluids. The output data is a percent weight change of thesealant material in both the bare (FIG. 14A) and in application (betweentwo aluminum alloy plates, FIG. 14B) configurations with about a 0.025″“exposure face.” A low percent weight change will correspond to goodresistance to the fluid in question and a high percent weight change tobe the converse. A change in either the positive or negative directionis relevant because it can indicate fluid absorption or material removalrespectively. The benefit this test shows is that Applicant's productsare resilient enough to continue functioning across a wide variety ofaviation environments. The data helps inform Applicant's recommendationsfor where certain products should be used based on their environment.This data shows these tested products to be resistant to degradationupon exposure to common aviation fluid, based upon 5% or under on bothbase and application: AGS silicone brake fluid, Royal Purple Synthetic,Isopropyl denatured ethyl, Dynalene EG and PG, and the de-icing fluid.This is based upon these initial tests only.

Smoke Density Smoke Density #5 #5 Jet A Fuel 12°/o 4°/o Autozone BrakeFluid 13°/o 4°/o Skydrol LD-4 30°/o 6°/o AGS Silicone Brake Flu  3°/o3°/o Royea 782 10°/o 4°/o White Mineral Oil  9°/o 5°/o Royal PurpleSynthetic  5°/o 4°/o Isopropyl Q0/₀ 1°/o Denatured Ethyl Q0/₀ Q0/₀Sky-Kleen 13°/o 4°/o Dynalene EG  3°/o 4°/o Dynalene PG  3°/o 4°/oDe-Icing Fluid PA  3°/o 4°/o De-lonized Water Q0/₀ Q0/₀ Mobil Aero HF15°/o 4°/o 5% NaCl Solution  2°/o 1°/o Potassium Formate  4°/o 3°/o

FIGS. 8A-8C illustrate a cabin interior 60 that includes a floorboardassembly 62. Floorboard assembly 62 is provided as a support surface forpassengers to walk on and as a support for other structures. Wheremultiple floorboards 63 join frame subassembly 64, there is typicallyengagement between the underside of the individual floorboards and theindividual members or stringers 65 of the frame subassembly 64. Priorart elastomeric tape has been used to support thefloorboards/subassembly joint in an environmentally sealing manner. Inone application of tape 26 described herein, the sealant with the novelqualities set forth herein is used between the floorboards and the framesubassembly to impart both an environmental seal as well as beneficialfireworthy properties as set forth herein.

Although the invention has been described with reference to a specificembodiment, this description is not meant to be construed in a limitingsense. On the contrary, various modifications of the disclosedembodiments will become apparent to those skilled in the art uponreference to the description of the invention. It is thereforecontemplated that the appended claims will cover such modifications,alternatives, and equivalents that fall within the true spirit and scopeof the invention.

The invention claimed is:
 1. An application for dispensing a sealanttherefore, the applicator comprising: a first compartment comprising afirst component; a second compartment comprising a second component; anda mixing nozzle having a tip; wherein the first component is a polyoland the second component is an isocyanate and wherein the twocomponents, when mixed in and emitted from the nozzle, form a cure inplace sealant that: has toxicity limits less than about 150 PPM HCN,1000 PPM CO, 100 PPM NO/N0 2, 100 PPM S0 2, 100 PPM HF, and 150 PPM HClunder AITM 3-0005, Issue 2; has a smoke density of 200 maximum at about4.0 minutes under AITM 2-0007A, Issue 3; and passes 12 second verticalburn test according to 14CFR part 25 subpart D, S25.853(a) compartmentinteriors.
 2. The application of claim 1 wherein the cured sealant has atackiness between about 5 and 50 psi.
 3. The application of claim 1wherein the sealant is 100% solids (no volatiles).
 4. The application ofclaim 1 wherein the cured sealant is elastomeric.
 5. The application ofclaim 1 wherein at least one of the first or second components includesa corrosion inhibiting composition.
 6. The application of claim 1wherein the cured sealant forms a non-adhesive, tight seal with analuminum aircraft part but is releasable therefrom.
 7. The applicationof claim 1 wherein cured sealant passes 3000-hour salt fog test (ASTM117).
 8. The application of claim 1 wherein the sealant cures toworkability within 30-90 minutes after mixing.
 9. The application ofclaim 1 wherein the volume of the first component is the same as thevolume of the second component.
 10. The application of claim 1 whereinthe cured sealant is cohesive.
 11. The application of claim 1 whereinthe cured sealant has a weight change of 30% or less upon exposure toaircraft fluids including at least one of the following sprays: Jet AFuel, Autozone Brake Fluid, Skydrol LD-4, AGS Silicone Brake Flu, Royea782, White Mineral Oil, Royal Purple Synthetic, Isopropyl, DenaturedEthyl, Sky-Kleen, Dynalene EG, Dynalene PG, De-Icing Fluid PA,De-Ionized Water, Mobil Aero HF, 5% NaCl Solution, Potassium Formate.